Update. This problem reoccurred today, with all Zwave control lost and last cloud backups have failed citing "Zwave" as the cause.
Since running this procedure in the link below 9 days ago to fix the first occurrence, I've updated to 2.3.8.133 on my C7.
I tried shutting down the hub and removing power, this time it fixed the issue.
If there is anything I can do to further troubleshoot the root cause either now or if this happens again, please let me know.
